Is Whole Grain Bread Healthier Than White Bread

Although many people have studied which bread is the healthiest, it is still not clear how the differences of different types of bread affect clinically relevant parameters and microbiota. In the journal ‘Cell Metabolism’ on June 6, researchers from the Weizmann Institute published the results of a comprehensive randomized comparison clinical trial of 20 healthy participants, comparing the impact on their health between eating processed white bread and handmade whole grain bread.

Surprisingly, the researchers found that the bread itself did not significantly affect the participants, and different people had different reactions to the bread. The research team then devised a method to help predict an individual's possible response to the bread in the diet.

10% of the calories consumed by all participants in the study came from the bread. Half of the participants were asked to consume more processed bagged white bread within a week, which they consume about 25% of calories from; and the other half were asked to consume more fresh whole grain bread baked specifically for the study. Afterwards, they stop eating bread for two weeks, and then reversed the bread consumption of the two groups.

Before and during the study, the researchers monitored various health effects of the participants, including waking blood glucose levels, the concentration of the main minerals calcium, iron and magnesium, cholesterol and fat levels, kidney and liver enzymes, along with the signs of inflammation and tissue damage. The researchers also measured the microbiota composition of the participants before, during and after the study.

Eran Segal, a computational biologist at the Weizmann Institute of Science, said: "The initial findings did not match our expectations. The finding is that there is no significant clinical difference in the effects of the two types of bread on the participants we measured. We monitored various health indicators. However, there is no measurable difference in the effects of this dietary disturbance."

In their previous work, they found that different people response with different blood sugar levels to the same diet. Based on this, the researchers suspect that there may be more complicated things: perhaps the blood sugar response of some people in the study is better for some kinds of bread, and some people are better for another kind of bread. Further study showed that this was really the case. About half of people responded better to processed white bread, while the other half responded better to whole grain bread. The lack of difference is found when all the findings are averaged together.

Eran Elinav, a researcher in the Immunology Department of the Weizmann Institute, said: “The findings of this study are not only fascinating, but also potentially important, because they point to a new paradigm: different people respond differently to the same food. So far, the nutritional value assigned to food is based on a small number of scientific studies, which unfortunately does not hold true in this case."

He added: "This discovery will help to research more reasonable methods to tell people which foods are more suitable based on their microbiota."

Professor Avraham Levy of the Department of Plant and Environmental Sciences warned of the study: “In these experiments, participants were required to eat exactly the same amount of sugar in the bread, which means they ate more whole grain bread because whole grain bread contains fewer sugar. In addition, we know that because of the higher fiber content of whole grain bread, people generally eat less whole grain bread. We did not decide how much to eat based on how full you are, so research will continue to get on."